PORTSMOUTH — On April 24, 2012, an employee of the Redhook Ale Brewery in Portsmouth was fatally injured when a plastic keg he was cleaning with pressurized air exploded.

In the aftermath of the accident, investigators from the Occupational Safety and Health Administration visited Redhook's facility to document the circumstances. They recently released the following photographs: (story continued below photos)

The remnants of an exploded plastic keg are seen inside the Redhook Ale Brewery in Portsmouth following an accident that left a worker dead in April 2012.

Protective eyewear is seen on the ground near the spot where the keg ruptured.

The bottom half of the keg is seen resting on a conveyor belt near the keg purging station.

The bottom half of the keg is seen close up.

The two halves of the exploded keg rest approximately 20 feet apart.

The top half of the keg is seen up close. The keg was owned by Saint Arnold Brewing Company in Texas, according to OSHA investigators. It was delivered to Redhook in error as part of a shipment of empty kegs being returned.

The keg split into two halves at the middle seam, striking 26-year-old employee Benjamin Harris in the head and chest.

The accident took place at about 7 a.m. in a storage and supply area of the Redhook facility, which is located beside a brewery and pub at Pease Tradeport.

The keg involved in the accident was manufactured by a company called Plastic Kegs America. It was not owned by Redhook. The keg was delivered to Redhook in error as part of a delivery of empty keg returns. Harris was emptying the keg in order to stack it on a pallet when it ruptured.

In the wake of the accident, some brewery owners began to cast a wary eye toward plastic kegs. Foster's has documented at least four other instances in which products manufactured by PKA have exploded at breweries. An instance was also documented on the website of the Consumer Product Safety Commission.

OSHA concluded the brewery's keg washing equipment was operating at a pressure that exceeded the maximum threshold recommended by the manufacturer of the plastic keg. The keg was rated with a maximum pressure of 60 pounds per square inch (PSI), according to OSHA investigation documents.

Stainless steel kegs, the standard vessel used in the brewery industry, are also commonly rated at a maximum pressure of 60 PSI, according to OSHA.